The present embodiments relate generally to wellbore treating fluids introduced into a subterranean zone penetrated by a wellbore, particularly fluids introduced as remedial compositions such as pills.
Conventionally, a wellbore is drilled using a drilling fluid that is continuously circulated down a drill pipe, through a drill bit, and upwardly through the wellbore to the surface. Typically, after a wellbore has been drilled to total depth, the drill bit is withdrawn from the wellbore, and circulation of the drilling fluid is stopped, thereby initiating a shut-down period. The drilling fluid is left in the wellbore to provide hydrostatic pressure (i.e., hole stability) on permeable formations penetrated by the well bore, thereby preventing the flow of formation fluids into the wellbore. Another function provided by the drilling fluid left in the wellbore is to prevent lost circulation, by sealing off the walls of the wellbore so that the drilling fluid is not lost into highly permeable subterranean zones penetrated by the wellbore. Sealing off the walls of the wellbore is typically accomplished during the shut down period by the deposit of a filter cake of solids from the drilling fluid, and additional dehydrated drilling fluid and gelled drilling fluid, on the walls of the wellbore.
The next operation in completing the wellbore usually involves running a pipe string, e.g., casing, into the wellbore. After the pipe is run in the wellbore, the next operation typically involves cleaning out the wellbore, which may be accomplished by re-initiating circulation of drilling fluid. After clean-up operations are performed in the wellbore, primary cementing operations are typically performed therein. Namely, the pipe is cemented in the wellbore by placing a cement slurry in the annulus between the pipe and the walls of the wellbore.
During any of the above or other operations performed in the wellbore, a number of problems can occur that require remedial operations. One such problem is lost circulation. Lost circulation occurs when the drilling fluid is “lost” into the subterranean zone penetrated by the wellbore. The drilling fluid can be lost when the drill bit encounters spaces such as fissures, fractures, or caverns in the subterranean zone, and the drilling fluid flows into such spaces. Lost circulation can also occur when the hydrostatic pressure provided by the drilling fluid in the wellbore is compromised. This occurs when the drill bit encounters other types of “spaces”, such as unfavorable subterranean zones, which may be comparatively low pressure subterranean zones, such as vugs, fractures, and other thief zones, and similarly, comparatively high pressure subterranean zones. When lost circulation occurs, remedial steps are required.
Most remedial steps for lost circulation comprise introducing a remedial composition into the wellbore to seal the above-described spaces. Examples of such remedial compositions comprise mixtures of clay and aqueous rubber latex or hydratable polymer (e.g., U.S. Pat. Nos. 5,913,364; 6,060,434; 6,167,967; 6,258,757), which form masses with a consistency often referred to as “rubbery”, “viscous”, or “gelatinous”, to seal the space. Exemplary remedial compositions form such masses upon contact with drilling fluid, mud or other compositions with which the remedial composition is designed to react, thereby sealing fractures, fissures, low pressure or high pressure subterranean zones, and the like. Such remedial compositions are often referred to as a “pill” by those of ordinary skill in the art.
The present embodiments provide compositions in the form of remedial compositions, such as pills, that comprise zeolite, as well as methods for the use of such remedial compositions comprising zeolite.